Adverse remodeling of the myocardium after myocardial infarction speeds progression to heart failure. While cell therapy has been met with great enthusiasm, there are numerous shortcomings that prevent long-term functional improvements. Moreover, these cells come from diseased individuals and immunogenicity limits most studies to autologous therapy. Finally, it is widely believed that the main effect of cell therapy is mediated by paracrine effectors and not the cells themselves. We have isolated rat and human cardiac progenitor cells that are cardiac-derived, express c-kit, do not express any markers of cardiogenic lineage, but can differentiate in to all cardiac cell types. These cells basally release microRNA (miR) in to the extracellular space. When treated with hypoxic conditions, these cells increase cardioprotective miRs within exosomes. Preliminary studies demonstrate that these hypoxic exosomes enhance endothelial cell tube formation and decrease fibrotic gene expression in fibroblasts. Therefore, the objective of this proposal is to examine the protective/regenerative capacity of these exosomes in rat models of ischemia-reperfusion. Additionally, with a large number of patient samples from children and adults, we can perform multivariate analysis to examine the factors that affect various in vivo mechanisms. Factors include patient age, gender, and exposure to hypoxic conditions. Completion of the proposed studies will determine whether hypoxic exosomes are a beneficial therapy for ischemia-reperfusion injury, as well as determine potential patient factors that contribute to these responses.